1. Field of the Invention
The present invention relates to a recognition dictionary system and a recognition dictionary system updating method used for, for example, an on-vehicle navigation system.
2. Background Information
In recent years, numerous systems have been offered that conduct speech dialog with a user by speech recognition. In the basic flow of speech dialog, speech is input to a system in order to accomplish a user's objective, and then a response that corresponds to the results of the system's recognition of that speech is presented to the user via speech or a display device. If sufficient information for accomplishing a task (the user's objective) is obtained with a user's single utterance, then a process, such as the operation of a device, is executed based on that information. However, if sufficient information is not obtained, then the system aims to accomplish the task by conducting a dialog, which includes questions and responses as well as the repetition of utterances, until sufficient information is obtained. A representative application of conducting speech dialog with a user is a recognition dictionary system included in a navigation speech recognition system whose main task is the input of a destination facility name into a navigation device.
In a conventional navigation speech recognition system, a user utters a facility name, which constitutes the destination, in accordance with a message that is presented by a display or the speech of the system. The conventional navigation speech recognition system then sets the destination by checking the recognition dictionary for this uttered speech, and outputting the term that is the closest match (the one with the highest recognition score) as the recognition result. This conventional speech recognition method, which sets the term (1-best) included in the recognition results that has the highest recognition score as the recognized term, is the simplest method. The goal of applying speech recognition to more complex tasks or to systems that have a large number of terms has led to the proposal of a technique that re-evaluates the acceptance of a recognized word based on a so-called “confidence measure” (CM). The confidence measure is an index that expresses how easily a term might be mistaken for a rival term. Various methods for representing the confidence measure have been proposed that use, for example, a posterior word probability, an N-best list and a word lattice (F. Wessel, R. Schluter, and H. Ney. “Using Posterior Word Probabilities For Improved Speech Recognition”, in Proceedings of the IEEE ICASSP 2000, Istanbul, Turkey, June 2000, pp. 1587-1590) (Japanese Laid-Open Patent Application Publication No. 2005-164837).
Furthermore, combining the confidence measure and a dialog strategy makes it possible to implement a task accomplishing method that is based on high-level dialog. With a dialog in which, for example, a destination is set in the navigation speech recognition system discussed above, the user utters the speech, “XX golf course”, whereupon the system first attempts a nationwide search for facilities. However, there are cases in which a sufficient confidence measure cannot be obtained because of the large number of rival terms. Accordingly, the system pursues a response strategy that asks for the prefecture name, and then re-executes the search, this time focusing on the term, which was obtained based on the user's input of the prefecture name, and thereby accomplishing the setting of the destination.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved recognition dictionary system. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.